In ten NIH-supported core projects conducted by the 9 co-investigators of this proposal, fluorescence spectroscopy provides a unique window into dynamic aspects of protein conformational transitions accompanying peptide-membrane interaction and insertion, nucleic acid- protein interaction, and investigations of the active conformation of drug molecules bound to their protein or nucleic acid targets. We seek to acquire a state-of-the-art fluoresc4ence spectrometer to support and enhance these research programs. This instrument would replace an aging fluorescence spectrometer that is now prone to breakdown. Also, it is controlled by an obsolete, non-Y2K-compliant computer for which replacement parts are unavailable. The existing instrument has been operated as part of a shared facility for approximately 6 years; in that time it has served more than 20 investigators from in 8 departments and 4 divisions of this University, and over time has provided support to 20 or more NIH-supported projects. The instrument to be purchased will be equipped to enable fluorescence anisotropy measurements, and will have a stopped-flow accessory to support those projects requiring rapid kinetics measurements. Diode array detectors and dual monochromators will enable rapid acquisition of entire spectra at short time scales. Absorbance measurements will be possible, enabling the monitoring of self-assembly reactions or aggregation. This instrument will support a principal group of 7 NIH-supported investigators and two additional core investigators and two additional core investigators. Among them there is both have extensive, demonstrable need, as well as experience with fluorescence and stopped-flow techniques. The transition to modern, reliable instrumentation with computer-controlled data acquisition will not only make possible experimental approaches that are not feasible with the existing instrument, but also enhance productivity by reducing down time for repairs and the fairly constant drain of time devoted to scavenging functional parts for the obsolete computer system. Over all, extensive computer-controlled data acquisition, rapid data acquisition, and stopped-flow fluorescence represent capabilities that will enhance greatly the existing NIH0-supported projects.